ReadOnly Property or property with private set I should use in vb.net?

Question

I Like .NET automatic properties, in C# it so easy to declare readonly property by declaring its set section as private like this:

public String Name{ get; private set; }

But when I tried that in VB.NET I was shocked that it is not supported as mentioned here and I have to write it as follows:

Private _Name as String
Public ReadOnly Property Name as String
   Get
      return _Name
   End Get
End Property

Or:

Private _Name as String
Public Property Name as String
   Get
      return _Name
   End Get
   Private Set(value as String)
      _Name = value
   End Set
End Property

What the difference between these declarations in VB.NET, which one is preferred and Why?

Edit

Which one will affect compile time, runtime or performance at all?

Grant Thomas · Accepted Answer · 2012-01-26T16:54:55.797

In the case of ReadOnly, only those with access to the underlying variable may change the underlying value (i.e. elements within the same class, for instance) by directly applying such a change. In the latter case, Private Set - this is much the same - elements within the scope of the class can change the underlying value, but can do so by means of the property.

Which one is preferred is circumstantial: one advantage of properties is that you can, like a method, have further implementation involved when applying the change (although side-effects should be avoided, you might 'validate' and take exception, for instance). If there is always something else to do when setting the value, that is strongly related to setting the value, you might do it within this property setter, as opposed to having to code that implementation everywhere you do the set.

score 2 · Answer 2 · answered Sep 29 '18 at 12:44

Note that if you are using the Roslyn compilers (.NET 4.6 and higher, VS.NET 2015+), then even when the short VB.NET form is used

Public ReadOnly Property Name as String

with no private variable, constructors for the class are still allowed to assign values to the readonly property. You can even pass the property to other functions as a ByRef parameter.

Public Class SomeClass
    Public ReadOnly Property Name1 As String
    Public ReadOnly Property Name2 As String
    Public Sub New()
        PrivSub(Name1)
        Name2 = Name1 & " is now"
    End Sub
    Private Sub PrivSub(ByRef n As String)
        n = System.DateTime.UtcNow.ToLongDateString()
    End Sub
End Class

DotNetFiddle of this class

score 1 · Answer 3 · answered Jan 26 '12 at 16:48

the first block will only allow you to get the value of Name. you cannot set Name.

the second block allows you to set the value of Name from within the class. example:

Me.Name = "new value"

I would choose option 1 because the second option verbose without providing any real value.

score 1 · Answer 4 · answered Jan 26 '12 at 16:58

The first property declaration ReadOnly makes it so the property cannot be modified at all. The second Private Set allows the property to be modified within the class you are working in Me.Name = "str".

In both cases the underlying value can still be changed within the class using _Name = "str".

ReadOnly Property or property with private set I should use in vb.net?

4 Answers4